1. Field of the Invention
The present invention relates generally to the field of whirlpool bath systems of the type having a plurality of venturi jets and a centrifugal pump. The invention relates more specifically to the centrifugal pump of such systems and to certain improvements which result in greater efficiency, reduced noise and easier fabrication.
2. Prior Art
A centrifugal pump design for whirlpool bathtubs has two areas of deviation from most pump designs. First is that the outlet is centered, rather than tangential, to allow the pump to be placed against the tub back slope in either direction. Secondly, the inlet is lowered and includes a passageway for the water that would normally remain in the volute to drain back into the suction (inlet) line when the bathtub is drained. Both of these design criteria create challenges in the design to gain optimal efficiency of the pump. Here we look at the second challenge and a resulting solution.
The challenge in the inlet design is due mainly from manufacturing considerations. A cost effective plastic injection mold requires that the internal features of the part be made on cores that pull out in orthogonal directions. This requirement contrasts strongly with the requirement that the shape of the inlet be a smooth transition from the lowered pump inlet to the impeller entrance. There should be no sharp points to create turbulence as the water passes. If the inlet diameter is larger than the impeller entrance diameter, the transition to the smaller diameter should be smooth and continuous along the skewed inlet axis without enlargements in cross section along the way. A design with either of these elements, while functional, will cause a loss of efficiency and produce undesirable noise.